Internal combustion engines having a turbocharger are generally known. In EP-A-0 869 275 it is disclosed that a useful technique in the control and reduction of undesirable emissions from internal combustion engines is the use of pressure-charged intake air. This may permit the use of relatively smaller cubic displacement and lighter weight internal combustion engines, reducing in turn the specific fuel consumption and overall mass of the machine to perform a given function. In addition to the benefits of reduced size and mass, the typical pressure-charging device may be controlled to provide improved emissions characteristics. Pressure-charging machines suitable for such applications may include an exhaust gas driven turbocharger that may typically include an exhaust gas driven turbine linked to a compressor disposed in the intake air stream to provide pressure charged combustion air. The typical turbocharger may be controlled by providing a waste gate valve that may control the exhaust gas flow and gates exhaust gas to bypass the exhaust gas turbine and control the charging rate of the turbocharger so that the maximum pressure limits of the associated internal combustion engine are not exceeded. EP-A-0 869 275 does not disclose how the waste gate exhaust valve operates.
A disadvantage of known valves for controlling the exhaust gas flow to the turbocharger is that they are vulnerable to dirt. Especially, in applications in which the fuel used in the internal combustion engine is not very clean, for example in crude oil or heavy fuel applications, contamination of the known valve may lead to malfunctioning of the valve and, consequently, to damage of the internal combustion engine by overload. No waste gate valves are known by us for use in conjunction with large Diesel engines having medium rotating speed, for example 400-1200 rpm, and burning crude oil and heavy fuel. Such engines may have piston diameters in the range of 200 mm to more than 600 mm and may range in power from, for example, 1000 kW to 16000 kW.
Another disadvantage of known valves for controlling the exhaust gas flow to the turbocharger is that the parameter by which they are controlled is the exhaust gas pressure. Consequently, the control arrangements of the valve are likely to be contaminated by the hot exhaust gas. In view thereof, the durability of the known exhaust gas regulating valves is limited.
Additionally, known waste gate valves may, in general, not be able to adjust the amount of exhaust gas that may be diverted away from the turbocharger. In most cases, the known waste valve arrangements are either opened or closed. Known valves do not provide more than one control range. The outside air temperature and the outside air pressure may have a large influence on the charge pressure. Known exhaust valve arrangements do not take account of varying outside temperatures and pressures. Known waste gate valves are dedicated devices, having a specific application range that can not be varied easily. Because the control assemblies of the known valves are in contact with exhaust gas, those parts should be able to withstand extreme heat. Consequently, the known waste gate valves are expensive.
The current disclosure aims to alleviate or overcome these disadvantages associated with the prior art.